This invention relates to components for gas turbine engines. More particularly this invention is concerned with the surface treatment of gas turbine engine components and a method for producing such blades.
Gas turbine engine components and in particular aerofoil blades and vanes are susceptible to damage caused by foreign object ingestion and general fatigue. Such damage may result in stress concentrations and cracks which limit the aerofoils life. One known solution is to increase the thickness of the aerofoil in the leading and trailing edges which are most susceptible to damage. However this adds weight and adversely affects the erodynamic performance of the aerofoil and reduces the efficiency of the engine.
It has also previously been proposed to introduce regions of residual compressive stress into the aerofoil and ideally through section compression to reduce the tendency of crack growth. By creating such xe2x80x98through thickness compressionxe2x80x99 whereby the residual stresses in the edges of the aerofoil are purely compressive, the tendency for cracks to grow is severely reduced. The stress field is equalised out in the less critical remainder of the aerofoil.
Prior U.S. Pat. Nos. 5,591,009 and 5,531,570 disclose a fan blade with regions of deep compressive residual stresses imparted by laser shock peening at the leading and trailing edges of the fan blade. The method for producing this fan blade includes the use of multiple radiation pulses from high power pulsed lasers producing shock waves on the surface of the fan blade. However the processes disclosed in these prior patents have a number of disadvantages. The magnitude of stress that can be induced is limited and the penetration of depth of these stresses is also limited while the process is generally time consuming and costly. Laser shock peening can typically provide a penetration depth of 1 mm.
It is an aim of the present invention, therefore, to provide an improved gas turbine engine component which is longer lasting and better able to withstand fatigue and/or foreign object damage.
According to the present invention there is provided a component one or more surfaces wherein at least one of said surfaces comprises an ultrasonic hammer peened surface and wherein a region of deep compressive residual stress caused by ultrasonic hammer peening is provided in said treated surface.
Also according to the present invention there is provided method of ultrasonic hammer peening a component comprising the step of ultrasonic hammer peeing at least one surface of said component so as to provide a region of deep residual compressive stress.
Also according to the present invention there is provided a method of ultrasonic hammer peening a gas turbine aerofoil blade or vane comprising the step of ultrasonic hammer peening at least one of the leading and trailing edges of said blade or vane on at least one of the suction and pressure sides thereof.